Amazon.com (AMZN 3.21%) has entered into a deal to purchase its Seattle based headquarters, which it currently leases from Vulcan Real Estate. The online retailer filed an SEC notice today, indicating that the 11 buildings that make up the Seattle campus will be purchased at the end of 2012 for $1.16 billion.

The Amazon campus covers 1.8 million square feet and is located north of downtown Seattle near Lake Union. The Seattle Times has reported that Vulcan put the property on the market earlier this year but didn't necessarily expect a bid from Amazon. The resulting deal equates to $644 per square foot and ranks as the second highest cost-per-foot commercial sale in Seattle.

To close the deal, Amazon has put down a $23 million deposit, which will increase to $51 million near the end of October. If the deal is not completed by the end of the year, that deposit will be forfeited.